Tropical Storm Melissa continued Thursday its slow push north in the Caribbean, expected to grow into a major hurricane as it nears Jamaica, but its long-term path including what effects it might have on Florida remain uncertain, according to the National Hurricane Center.

In the NHC’s 8 a.m. advisory, Melissa had maximum sustained winds of 50 mph and was located about 215 miles southeast of Kingston, Jamaica and about 275 miles southwest of Port au Prince, Haiti moving northwest at 5 mph.

“A slow northwest or north motion is forecast during the next couple of days, followed by a westward turn over the weekend,” forecasters said. “On the forecast track, Melissa is expected to be nearer to Jamaica and the southwestern portion of Haiti during the next couple of days.”

A hurricane watch was issued for Jamaica on Thursday and continued for the southwestern peninsula of Haiti from the border with the Dominican Republic to Port-Au-Prince. Jamaica is also under a tropical storm warning.

Tropical-storm-force winds extend outward up to 115 miles from the center.

“Little change in strength is expected during the next day or so, but significant strengthening is expected by late Friday and over the weekend. Melissa is forecast to become a hurricane in a couple of days,” forecasters said.

The system is forecast to intensity to a Category 1 hurricane with 80 mph sustained winds and 100 mph gusts by Saturday. The five-day forecast has it growing to a Category 3 major hurricane by Sunday with 115 mph sustained winds and 140 mph gusts and intensifying further to Category 4 by Monday with 130 mph sustained winds and 160 mph gusts.

The National Weather Service in Melbourne has its eye on the system.

“Some uncertainty continues late weekend and into next week on the track of Tropical Storm Melissa and the amount of moisture present over the Florida peninsula,” NWS forecasters said. “Fortunately, model consensus keeps Melissa well to the south of the Florida peninsula through at least the next 5 days. However, any storm in the Caribbean bears watching for the local area and residents and visitors should continue to monitor official National HurricaneCenter updates.”

Hurricane conditions could begin affecting Haiti on Thursday with tropical-storm conditions in Jamaica on Thursday or Friday.

The slow-moving storm could bring dangerous rainfall to southern Haiti, southern Dominican Republic and eastern Jamaica through Saturday with 5-10 inches expected through Friday, and potentially more depending on the storm’s path. Areas of significant flash flooding and mudslides are possible.

Another 2-4 inches are forecast across Puerto Rico, northern Dominican Republic, northern Haiti and western Jamaica.

Melissa, which formed on Tuesday, became the 13th tropical cyclone of the season.

Four so far have grown into hurricanes, and three of those became major hurricanes. Only one, Tropical Storm Chantal, made a U.S. landfall this year.

Hurricane season runs from June 1-Nov. 30.